Pressure vessels are commonly used for containing a variety of fluids under pressure, such as storing hydrogen, oxygen, natural gas, nitrogen, propane and other fuels, for example. Suitable container materials include laminated layers of wound fiberglass filaments or other synthetic filaments bonded together by a thermosetting or thermoplastic resin. A polymeric or other non-metal resilient liner or bladder often is disposed within the composite shell to seal the vessel and prevent internal fluids from contacting the composite material. The composite construction of the vessels provides numerous advantages such as lightness in weight and resistance to corrosion, fatigue and catastrophic failure. These attributes are due to the high specific strengths of the reinforcing fibers or filaments that are typically oriented in the direction of the principal forces in the construction of the pressure vessels.
FIGS. 1 and 2 illustrate an elongated pressure vessel 10, such as that disclosed in U.S. Pat. No. 5,476,189, which is hereby incorporated by reference. Vessel 10 has a main body section 12 with end sections 14. A boss 16, typically constructed of aluminum, is provided at one or both ends of the vessel 10 to provide a port for communicating with the interior of the vessel 10. The vessel 10 is formed from an inner polymer liner 20 covered by an outer composite shell 18. In this case, “composite” means a fiber reinforced resin matrix material, such as a filament wound or laminated structure. The composite shell 18 resolves all structural loads and liner 20 provides a gas barrier.
When a pressure vessel is exposed to intense heat, as in the case of a fire, the heat increases the pressure of the gas in the vessel. In a typical steel vessel, one or more rupture discs are provided in a valve body at the end port of the vessel. These discs react to the pressure increase to release gas before the tank ruptures.
In the case of a composite vessel, however, the composite does not heat like steel and thus the pressure does not rise in the tank in the same manner (so that a pressure release valve actuated by an increase in pressure is not appropriate). However, upon continued exposure to heat, the pressure in the composite vessel increasex, ultimately causing a rupture, thereby resulting in an uncontrolled release of gas and/or an explosion.
In the prior art, a plurality of temperature sensors are positioned at discrete locations along a tank. Such sensors are operably coupled to one or more pressure relief valves for the tank. Such coupling may be accomplished electrically, chemically, mechanically, or by a pressurized line. In an example, a plurality of discrete sensors are fastened into a pressurized tubing that runs along the outside of the tank. However, some authorities regulating the transportation of certain goods (e.g., high pressure gas) discourage the use of lines or manifolds that are pressurized during transportation. Moreover, the use of sensors positioned at discrete locations on a tank leaves portions of the tank that are free from sensor coverage.